Healthy volunteers who have no history of speech, swallowing or breathing problems and patients who have difficulty swallowing because of a neurologic disorder, musculoskeletal disease or head and neck cancer that caused tongue weakness and dysphagia may be eligible for this study. Such medical conditions may include stroke, Parkinson's disease, multiple sclerosis corticobasal degeneration, progressive supranuclear palsy, Gaucher's disease, leukodystrophy, cerebral palsy, myositis, or mouth, throat or neck cancer. Volunteers who have not participated in a NIH protocol for 1 year will be screened with a brief medical history and physical examination. Dysphagic patients not currently enrolled in a NIH protocol will also have a brief medical history and physical examination. In addition, they will have a modified barium swallow to determine the nature and degree of their swallowing difficulty.